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Death of a VC

Discussion in '80-Series Tech' started by landtoy80, Oct 22, 2003.

  1. landtoy80

    landtoy80

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    I have several ideas why the VC goes in the HF2AV.
    My old VC will lock up when heated with a torch.
    The t-case would get really hot and lock the VC while driving at 65+mph on hot days.
    It even got hot enough to lock the VC with the front driveshaft off and the diff lock switch locked.
    This happened after I put MI 75w90 in it. That stuff is like water. I haven't had time to get a dino 75w90 to see how thick it is compaired to the M1.
    I think maybe the thinner M1 oil was to thin for my old 206k mi t-case and the bearings were not getting lubed enough and were getting hot enough to lock the VC.
    As it is NOT summer any more up here, I need a victim from the SW with a IR temp reader thingy. They need to drive at 70+ on a hot 80f+ day and take some temps.
    I will heat up my bad VC and take temps and see how hot it is when it locks.

    But I will need a victim to help me.
     
  2. IdahoDoug

    IdahoDoug

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    Reducing friction is one of synthetic lube's key improvements. Friction = heat. I suspect it was simply time for the VC to go, perhaps from a PO running it at higher speeds with different diameter F/R tires for a long time, and it happened to fail when it had M1 in it. If anyone has had their 80 since new and can be sure it was not run with different F/R tires (it is common for people to buy 2 new ones and put them on the front) AND has had a VC failure, I'd be interested to hear about it.

    Doug
     
  3. landtoy80

    landtoy80

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    The t-case got super hot the last time I drove it. It took 3hrs and a hose to cool it so it would unlock. This is why I want to see what a t-case operating temp is. It might of been the t-case bearings and not the VC???
     
  4. Cruiserdrew

    Cruiserdrew SILVER Star

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    I hope it isn't the Mobil 1. Mine has run that the last 50k with no complaints, but I'm at less than 1/2 of Kurt's mileage. I did think my fuel mileage improved with the Mobil 1 in the transfercase. That has to mean less friction loss and thus less heat. I have switched my other cruisers over to Chevron Delo Gear oil but the 80 calls for 75w-90 and the Delo is 80w-90. The Delo smells better if nothing else.
     
  5. IdahoDoug

    IdahoDoug

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    Kurt,

    There's a worthwhile exercise you might do as a hard data point. Lift your tires one at a time and measure the circumference. Be as precise as you can right down the center line of the tire tread.

    Even new tires have some variation, and this could be the source of your problem. If your TC is heating up that much, I can almost with complete confidence tell you that the source is not your VC. Why? For the VC to generate so much heat that it is heating up a thermal mass the size of the TC, the VC itself would have to be hot beyond belief. In addition, one the VC locked up, it would no longer be generating the heat of friction, and you would not expect the TC itself to have heated up much at all by that point.

    I'd also drain some oil and send it to an oil analysis company. The cost of this simple everyday test pales compared to trashing your center diff. They can tell you what metals they find, and what they think it means. Be sure they know it's an entirely gear driven center diff, NOT a TC by the way.

    I'll tell you my suspicion. If the rear driveshaft splines are overgreased repeatedly or even once in a truly careless fashion, the hydraulic force is enough to compress the casing and distort bushings and bearings on the output end. This heating could be the final symptom before something seizes, which you've put off either by regularly changing the diff oil, and/or by putting Mobil 1 in. Analysis will immediately reveal if there's bearing material suspended in it.

    Doug
     
  6. landtank

    landtank SILVER Star

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    Don't forget that there is an oil pump with a filter screen in our t-cases. That kind of heat would make me beleive a lubrication issue. Pulling the front shaft and locking the diff would remove any friction from inside the VC.
     
  7. landtoy80

    landtoy80

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    There will be no oil testing on the old t-case as it is many pieces in a box now.
    The oil pump was working when I had the rear output shaft off.
    None of the bearings were blue looking.
    And with the center diff locked that rules out the VC for heat problem.
    I can't see it being a over greased driveshaft or there would be many more bad t-cases as all the JifflubeMarts use power geasers and over grease it all the time, but you kan't rule it out though.
    I just need to get a bottle of 75w90 dino and heat it up and see how it flows compaired to the M1. I find it strange that the M1 75w90 flows like water and dino 80w90 is like syrup.
     
  8. landtoy80

    landtoy80

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    I do need to add that M1 did leak out of my new t-case. Toyota did replace the t-case free of charge.
    As a side note my motor doesn't like M1 either. It sucks it at high rpms.
    Maybe its not the syn oil, I might just be M1:)
     
  9. landtank

    landtank SILVER Star

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    The more common heat source in a diff is actually the gears themselves. That is where most of the friction is happening, not so much the bearings, provided there is oil in there. Unlike a Ft or Rr diff where a simple oil bath can lubricate the gears I'm assuming it's the pump that gets the oil to the gears, especially the ones on the higher, input side of the t-case.
     
  10. cary

    cary

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    I don't think the Mobil 1 is the cause of your problems. Some common misconceptions:

    1) Synthetic is Thinner- It is not. If it was, it wouldn't be 75w-90, it would be 45w-50. 90 weight is 90 weight is 90 weight (within the 90 weight window there is slight variances). The 75w-90 will be slightly thinner at room tempurature than the 80w-90 because of the 75w cold rating.

    2) Synthetic is more slippery- Sorry, it is is not.

    3) It is more prone to leak- yes and no. In old vehicles, synthetics with Esters (most do have some to keep the seals from shrinking) will have a mild cleaning effect. This cleaning effect will pull grunge away that may be plugging leaks. I bet if you filled that same brand new transfer case with mineral 75w-90 it would have liked.

    4) So why Synthetic- Base oils are more stable, it can sustain higher temps without breakdown, and will have more consistant performance through its life (mineral oil will thicken faster and have a higher cold start than Synthetic) and correspondingly has a longer life.


    Landtoy80- I think you truck was built the same day as Junks
    :'( :'(. Seriously, different vehicles respond differently to different oils. In my case I am using M1 0w-40 in the Landcruiser, BMW and Pathfinder and have no consumption in any. However as we discussed, your truck may be different. You will need to experiment. You may want to consider trying Redline 75w-90 gear oil in your diff, and Amsoil, Redline, or another Sythetic in your engine (or mineral like you are doing).

    Cary
     
  11. landtoy80

    landtoy80

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    I think 232,000mi in it has something to doo with it.

    Cary, I just put a tbs of M1 75w90 and a tbs of M1 15w50 on a bowl.
    The75w90 runs like water and the 15w50 is more like gear oil, it hardly flows.
    What gives???
    Shouldn't the gear oil be thicker than the 15w50?

    I did the test with M1 0w40 and they flow about the same with the 0w40 being a bit thicker :eek:
    This is at 45 to 50 f out side temp. and the oil is at the same temp as outside.
     
  12. IdahoDoug

    IdahoDoug

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    Kurt,

    The viscosity of a gear oil is different from the motor oil rating. Their cold flow characteristics are different, meaning the standard cold flow temp for gear oil's "W" viscosity might be lower than the rated temp of a motor oil due to their different tasks and the different environments they will operate in.

    IdahoDoug
     
  13. landtoy80

    landtoy80

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    Bummer, I was hopping M1 was going to pay for my t-case:(